linux-kernel - Re: [PREEMPT_RT] bogus lockdep assert from i915 on v5.2-rt1

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Message-ID: <alpine.DEB.2.21.1907162228030.1767@nanos.tec.linutronix.de>
Date:   Tue, 16 Jul 2019 22:29:53 +0200 (CEST)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Clark Williams <williams@...hat.com>
cc:     Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        RT <linux-rt-users@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PREEMPT_RT] bogus lockdep assert from i915 on v5.2-rt1

Clark,

On Tue, 16 Jul 2019, Clark Williams wrote:

> Thomas,
> 
> When looking at a problem on v5.2-rt1, I turned on lockdep and started getting warnings
> from lockdep_assert_irqs_disabled() in the i915 driver. They're making these calls inside
> a spin_lock_irqsave/spin_lock_irqrestore block, which of course doesn't fiddle with IRQs
> when PREEMPT_RT is configured. The attached patch places the three calls inside
> if (!IS_ENABLED(CONFIG_PREEMPT_RT_FULL)) blocks, so should avoid the bogus warning on RT.

AFAICT, all three asserts are pointless because there are already the lock
held asserts and lockdep will warn anyway when these locks are taken with
interrupts enabled.

Thanks,

	tglx